This invention relates to the use of micro-processors and micro-controller in the geophysical environment, and specifically the concept of embedding a micro-processor or micro-controller and the associated environment sensing transducers and compensation elements into every sensor or actuator element of a system.
There are many application areas where sensors are used to interact, monitor or generate signals to interrogate the external world. One such class of applications is geophysical instrumentation which use sensors to record natural fields from earth materials or depend on fields actively generated by actuators (sources) in order to interrogate the earth or buildings or other structures in a non-destructive manner. Such sensors are used in a wide variety of environments where temperature, pressure and other factors such as humidity, proximity to other materials, etc., can affect the operation of the sensors or actuators.
In some situations, the sensors, which are used in monitoring systems, can interact with the surroundings. The surroundings will have an effect on how the sensor works and modify the transfer function of the sensor. As a result the response which is observed from the sensor is variable depending on the material which it is in close proximity to.
When either the electronics in the devices themselves change their characteristics with temperature, pressure or any other factor such as voltage or humidity, then the response of the electronics of the system will cause errors in the observed results. Similarly if the sensors themselves have variable transfer functions depending on their means of deployment then the sensor (actuator) response observed will be in error unless the nature of the environment is known and the effect compensated for.
In some situations, the response of a transducer may be non-linear. Compensation can be applied by a micro-controller to linearize by feedback, by altering the sensor characteristics or by digital compensation after/before the sensor/actuator.
Therefore a means of sensing the change or the irregularity in the electronics, devising a digital means of compensating or modifying the output for the irregularity caused, and then providing an embedded control system for changing the overall actuator/sensor response in such a way as to keep it""s behavior invariant as its environment changes is desirable
An object of one aspect of the invention is to provide an improved microprocessor and micro-controller stabilized geophysical sensor and actuator.
Modern microcomputers and micro-controllers as well as peripheral components available in compact and inexpensive low-power circuits may allow for intelligent and adaptive sensors and actuators which may change with the surrounding physical conditions by providing stable (invariant) impulse response or may transfer functions over a wide range of conditions. The term sensor may be interpreted to imply either a sensor or an actuator. An actuator may cause the emission of a signal whereas a sensor detects such a signal.
Historically, geophysical sensors and signal conditioning circuits had to be designed to be insensitive to temperature, pressure and other properties by appropriate selection of components, and/or the use of nulling feedback circuits. In addition, sensor behavior could be affected by the fact that the surroundings influenced the fundamental sensor or actuator properties. For example, the capacitance of a small dipole antenna will change depending on the medium (material) it is placed in/on.
In accordance with one aspect of the present invention, there is provided an improved use of distributed intelligence in two broad but distinct manners.
Preferably the micro-controllers may distributed throughout the sensor and associated support electronics and may be interconnected through a communications bus in the most general situation. The micro-controllers may have the ability to extract information about the surrounding physical environment on a regular basis. The desired sensor behavior (impulse response or transfer function) may be defined. The sensor and associated circuitry response may be measured over the entire range of change of physical conditions anticipated for the sensor when used in real operation.
The micro-controller (possibly with the aid of an external computer) may learn how to adjust controllable circuit components so that the sensor output remains invariant and matches the desired output to within some predefined tolerance. The relationship between external conditions and sensor circuit properties are saved digitally in permanent memory accessible to the micro controller. Once xe2x80x9ctrainedxe2x80x9d, the intelligent sensor may be used in wide variety of conditions while exhibiting an invariant transfer function.
Conveniently the micro-controllers may operate in two manners; first they can modify the operating sensor circuit or sensor attributes; second, they may operate on the sensor input or output signals to achieve the desired behavior.
The breadth of the concept is enormous. One can easily visualize using this concept for the correction of a sensor that is temperature dependent. A micro-controller with a temperature measurement input and a knowledge of how the sensor output varies with temperature may be used to correct the sensor output with a look up table of correction factors. The most complex application may entail measuring multiple inputs concurrently and combining the results in a variety of fashions throughout a sensor assembly to achieve a desired result.
A major benefit of such systems is that they can be upgraded continually as better and smarter algorithms are devised. Automated training and self-calibration are obvious bi-products.